Awnings and similar fabric structures are typically constructed of a framework covered with a fabric or other flexible material. Over the years, the framework assembly has developed from wooden constructions to more advanced designs employing aluminum (or other light metal) extrusions with recessed fabric attachment zones. But despite the advantages offered by these extrusions, all heretofore known metal extrusions with recessed fabric attachment zones are functionally limited or become functionally defective when arcuately bent to form complex frame structures.
A number of present extrusions contain a recessed fabric attachment zone to which fabric is stapled or otherwise attached. In assembling a frame, such extrusions are either welded together or joined by means of mechanical fasteners. Subsequently, fabric is inserted into the recessed fabric attachment zone and secured by staples, tensioning clips or like methods. Typically, a pliable protective and/or decorative cap is wedged into the recessed zone to conceal and protect the joint.
When such extrusions are assembled into a plurality of straight sections, such a fabrication method generally works well. However, it is often desirable to form structures having curved surfaces wherein certain underlying and supporting extrusion members must be bent to a desired arcuate shape. Depending upon the relationship between the side of the extrusion containing the recessed attachment zone and the direction of curvature in the extrusion, the act of bending such an extrusion inevitably causes the recessed zone to inwardly collapse, thus impeding installation of the overlying fabric material and cap.
The inward collapse of the recessed attachment zone typically occur when the recessed attachment zone is oriented 90.degree. to the extrusion surface providing either a convex or concave bend. In such situations, the material along the outside of such a bend will be stretched and drawn to the inside of the bend, while the material along the inside of the bend will tend to compress and be forced to the outside of the bend. If the side containing the recessed attachment zone is between these opposing forces, the recessed attachment zone will be forced to a narrower opening due to the lack of any structural support across the opening. While this scenario would likely cause the greatest amount of distortion, a degree of distortion will occur in virtually any orientation of the recessed attachment zone when such an extrusion is bent.
If the inner attachment zone tends to close, or becomes significantly reduced in width, or becomes distorted while the extrusion is being formed into an arcuate shape, then it is only with great difficulty that the fabric covering and finishing trim pieces can be attached to this extrusion after it is incorporated into a frame for later fabric attachment.
Various solutions are known for dealing with this problem, such as inserting some form of spacing material within the inner attachment zone during the forming of the extrusion. This is not particularly practical, as the additional steps of inserting such spacing material prior to bending the extrusion, and then removing the spacing material, must be accomplished. This adds significantly to the labor and cost in forming such bends.
Another method used to maintain the proper recessed zone width during extrusion bending is to use bending devices, such as roll form benders or radiused die benders, which incorporate one or more tongues which may be inserted within the recessed attachment zone in order to lessen deformation. This is also a relatively costly process, as the bending tool must be modified to include such tongue extensions. Further, such tongues may roughen the interior edges of the recessed attachment zone as the extrusion is worked, thus possibly damaging the fabric covering.
The need arises for channeled extrusions for use in framed, flexible cover structures, which extrusions may be bent and formed in arcuate shapes. Such channeled extrusions must be capable of being bent or formed without deforming or narrowing the channel of the extrusion, and further without the requirement for specialized channel inserts or specially modified bending tools. Such extrusions would inherently provide for stability of the overall cross-sectional shape in bending by virtue of the shape and construction of the extrusion itself without becoming significantly distorted or deformed, particularly when the extrusion channel is located on a side parallel to the bending plane of the extrusion.